We will undertake to: isolate and characterize the 55,000-dalton plasma membrane (PM) acceptor protein for ADP-ribosylation carried out for the physiological -and cholera toxin- stimulated adynylate cyclase activities in cloned hepatocytes (RL-PR-C); reconstitution experiments with the 55,000-dalton protein and adynylate cyclase catalytic unit; transfer PM macromolecules from cell to cell, from isolated PM to cells, from the extracellular fluid to cells, and from liposomes to cells, all by biochemical fusion techniques; covalently attach radiolabeled peptide hormones to their cell surface receptors, and isolate the product by gel electrophoreses; study the biological role of hypothalamic insulin receptors; and to study the ontogeny of adrenergic receptors in dog kidney during development of the animal.